1. Field of the Invention
The present invention relates to a steering control apparatus for vehicle provided with a transmission ratio varying mechanism for varying a transmission ratio between a steering amount of a steering wheel and a turn amount of wheels.
2. Related Background Art
An example of the steering control apparatus provided with the transmission ratio varying mechanism of this type is disclosed in Japanese Laid-open Patent Application No. Sho 63-227472, for example. As disclosed in this application, the transmission ratio varying mechanism is provided with a driving motor and is constructed in such structure that a prescribed gear mechanism connects an input shaft connected to the steering wheel side to an output shaft connected to the tie rod side and that the transmission ratio of rotations between the input shaft and the output shaft can be changed by driving the gear mechanism by the driving motor.
On this occasion, the driving motor is controlled so that a rotational position of the driving motor detected by a rotational angle sensor approaches a target position computed based on the steering angle of the steering wheel and the transmission ratio.